A Yemeni judge has ordered the country's attorney general to produce a US citizen whose lawyers claim is a disappeared person.

Sharif Mobley, a US citizen arrested in Yemen in 2010 on since-dropped terrorism charges, has not been in contact with his lawyers since February 27. The Yemeni government denies that Mobley has been disappeared and is charging him with murder.

But according to Mobley's lawyers, with the UK-based human rights group Reprieve, Yemeni judge Abdelwali al-Shaabani has instructed attorney general Ali Alwash to bring Mobley to court for the next session in Mobley's trial, currently scheduled for August 20.

Mobley, from New Jersey, was not in court on Wednesday. He was also absent from a June 11 court hearing, and his wife has written to Barack Obama urging presidential intervention in the case.

In addition to wanting their client found, Mobley's legal team wants all charges against him dropped. The inability to locate Mobley "underlines the political nature of his detention", said his attorney Khalid al-Anasi.

“The Attorney General’s office failed to respond to the request the court made during the previous hearing and didn’t produce our client. The central prison told us that he is not in their possession, which means that they are trying to prevent us from meeting our client. We call for the investigation of the disappearance of our client, not just on this occasion but also when he was first detained by the authorities," Anasi said in a statement.

Reprieve said it is prepared to present "key evidence" of US complicity in Mobley's 2010 detention. While studying in Yemen with his family, Mobley was shot and detained by security forces and questioned by FBI agents during his convalescence.

Reportedly, US officials believed Mobley could help them track down al-Qaida preacher Anwar al-Awlaki, later killed in a drone strike. Yemeni officials say Mobley killed a hospital guard during a botched escape attempt.

The US State Department has declined to comment over Mobley's case, citing unspecified privacy considerations.